Use libproc instead of lsof on Darwin to detect live gcroots - #16439

#!/usr/bin/env bash

set -euo pipefail

testDir=$(mktemp -d)
holder=

cleanup() {
    if [[ -n "$holder" ]] && kill -0 "$holder" 2>/dev/null; then
        kill "$holder" 2>/dev/null || true
        wait "$holder" 2>/dev/null || true
    fi
    rm -f "$testDir/payload" "$testDir/hold"
    rmdir "$testDir" 2>/dev/null || true
}
trap cleanup EXIT

holderBash=$(command -v bash)
printf 'gc-runtime-test-%s-%s\n' "$$" "$RANDOM" > "$testDir/payload"
root=$(/run/current-system/sw/bin/nix store add-file "$testDir/payload")
mkfifo "$testDir/hold"

echo "active-nix=$(/run/current-system/sw/bin/nix eval --impure --raw --expr builtins.nixVersion)"
echo "holder-bash=$holderBash"
echo "disposable-path=$root"

# The empty argument exercises parsing of empty argv entries. The FIFO keeps
# this unentitled, Nix-built Bash process alive without starting a child that
# inherits GC_RUNTIME_ROOT.
env -i GC_RUNTIME_ROOT="$root" \
    "$holderBash" -c 'read -r value < "$1"' '' "$testDir/hold" &
holder=$!

sleep 1
kill -0 "$holder"

echo "delete-while-live:"
if /run/current-system/sw/bin/nix-store --delete "$root"; then
    echo "FAIL: Nix deleted a runtime-rooted path"
    exit 1
fi

test -e "$root"
echo "GOOD: deletion refused while holder was alive"

kill "$holder"
wait "$holder" 2>/dev/null || true
holder=

echo "delete-after-exit:"
/run/current-system/sw/bin/nix-store --delete "$root"
test ! -e "$root"

echo "PASS: Darwin environment runtime-root discovery works"